The present invention relates, in general, to valve guides, valve guide reamers, and, more particularly, maintenance and cleaning thereof. Generally, a variety of valves exist in an engine, such as camshaft cylinder, solenoid transmission, etc., for many different uses, such as automobiles, boats, aircraft, etc.
A common problem among engine valves, in particular in oil or gas infused valves is sticking, where there is buildup of deposits. Sources of the deposits are varied, including combustion by-products and oil contaminates. The lead salts that accumulate in the lubricating oil from the use of leaded fuels contribute to the deposit build up in the valve guides. They are mostly eliminated each time the oil and filter are changed. Depending on the amount of deposits, sticking between the valve stem and guide can restrict the valve movement and cause the valve to malfunction. This condition, where a valve is stuck or sticking occurs when contaminants in the engine lubrication oil or exhaust by products become deposited on the valve stems and guides, restricting the valve movement, and resulting in intermittent engine hesitation or miss. Factors exist that contribute to the rate of deposit accumulation, such as high ambient temperatures, reduced cool off time, and high lead content of fuel. If the valve is sticking or stuck, then cleaning is recommended. Similarly, many engine manufactures recommend cleaning as a routine preventative measure.
The exact clearance between a valve stem and the inner diameter of a valve guide is critical to proper operation. Because of this, valve guides are typically manufactured undersized to allow the inner diameter to be perfected after installation. The manufacturers of such valve guides typically make special reamers for initially perfecting this diameter after installation. These reamers are usually fluted and typically have a pilot portion near one end that has a diameter significantly less than the diameter of the finished valve guide. The pilot portion of these reamers is sized to fit the initial undersized inner diameter of the valve guide and thus ensure proper alignment before the larger diameter main portion of the reamer begins cutting the valve guide to its final perfected diameter. Cleaning is traditionally done with one of these reamers sized for use after initial installation of the valve guide, or put another way, with a reamer with a pilot section sized to fit the original undersized valve guide inner diameter. Although appropriate for initial installation, the significantly undersized pilot minor diameter is inappropriate for cleaning operations and causes the reamer to wander and misalign while it is being started and turned in the valve guide hole. This results in excess material removal and causes the valve guide hole to be deformed with a larger diameter than optimal at the end the reamer is started.
The purpose of cleaning a valve guide is to ream the inner diameter of the valve guide back to its initial conditions by removing deposited contaminants from the valve guide inner diameter. However, none of the reamers traditionally used for this operation have an appropriately sized pilot section to ensure proper reamer alignment so that only the deposits are removed without removing base metal material and distorting the valve guide hole.